Pen



FIG. 1 is a top front perspective view of a pen;

FIG. 2 is a side elevation view of the pen of FIG. 1;

FIG. 3 is a top elevation view of the pen of FIG. 1;

FIG. 4 is a back side elevation view of the pen of FIG. 1;

FIG. 5 is a bottom plan view of the pen of FIG. 1; and,

FIG. 6 is a top plan view of the pen of FIG. 1. 

The ornamental design for a pen, as shown and described. 